Method for making sheet-shaped heat and light source and method for heating object using the same

ABSTRACT

The present disclosure relates to a method for making the sheet-shaped heat and light source. An array of carbon nanotubes on a substrate is provided. A carbon nanotube film is formed by pressing the array of carbon nanotubes. A first electrode and a second electrode are electrically connected with the carbon nanotube film. Furthermore, a method for heating an object is related.

This application is a continuation application of U.S. patentapplication Ser. No. 12/006,301, filed on Dec. 29, 2007, entitled“SHEET-SHAPED HEAT AND LIGHT SOURCE, METHOD FOR MAKING THE SAME ANDMETHOD FOR HEATING OBJECT ADOPTING THE SAME,” which claims all benefitsaccruing under 35 U.S.C. §119 from China Patent Applications No.200710123809.3, filed on Oct. 10, 2007, in the China IntellectualProperty Office, the contents of which are hereby incorporated byreference.

BACKGROUND

1. Technical Field

The disclosure generally relates to sheet-shaped heat and light sources,methods for making the same and methods for heating objects adopting thesame and, particularly, to a carbon nanotube based sheet-shaped heat andlight source, a method for making the same and a method for heatingobjects adopting the same.

2. Discussion of Related Art

Carbon nanotubes (CNT) are a novel carbonaceous material and havereceived a great deal of interest since the early 1990s. It was reportedin an article by Sumio Iijima, entitled “Helical Microtubules ofGraphitic Carbon” (Nature, Vol. 354, Nov. 7, 1991, pp.56-58). CNTs areconductors, chemically stable, and capable of having a very smalldiameter (much less than 100 nanometers) and large aspect ratios(length/diameter). Due to these and other properties, it has beensuggested that CNTs should play an important role in various fields,such as field emission devices, new optic materials, sensors, softferromagnetic materials, etc. Moreover, due to CNTs having excellentelectrical conductivity, thermal stability, and light emitting propertysimilar to black/blackbody radiation, carbon nanotubes can also,advantageously, be used in the field of heat and light sources.

A carbon nanotube yarn drawn from an array of carbon nanotubes andaffixed with two electrodes, emits light, when a voltage is appliedacross the electrodes. The electrical resistance of the carbon nanotubeyarn does not increase as much, as metallic light filaments, withincreasing temperature. Accordingly, power consumption, of the carbonnanotube yarn, is low at incandescent operating temperatures. However,carbon nanotube yarn is a linear heat and light source, and therefore,difficult to use in a sheet-shaped heat and light source.

Non-linear sheet-shaped heat and light source, generally, includes aquartz glass shell, two or more tungsten filaments or at least onetungsten sheet, a supporting ring, sealing parts, and a base. Two endsof each tungsten filament are connected to the supporting ring. In orderto form a planar light emitting surface, the at least two tungstenfilaments are disposed parallel to each other. The supporting ring isconnected to the sealing parts. The supporting ring and the sealingparts are disposed on the base, thereby, defining a closed space. Aninert gas is allowed into the closed space to prevent oxidation of thetungsten filaments. However, they are problems with the sheet-shapedheat and light source: Firstly, because tungsten filaments/sheets aregrey-body radiation emitters, the temperature of tungstenfilaments/sheets increases slowly, thus, they have a low efficiency ofheat radiation. As such, distance of heat radiation transmission isrelatively small. Secondly, heat radiation and light radiation are notuniform. Thirdly, tungsten filaments/sheets are difficult to process.Further, during light emission, the tungsten filaments/sheets maybe needa protective work environment.

What is needed, therefore, is a sheet-shaped heat and light sourcehaving a large area, uniform heat and light radiation, a method formaking the same being simple and easy to be applied, and a method forheating an object adopting the same.

SUMMARY

A sheet-shaped heat and light source includes a first electrode, asecond electrode, and a carbon nanotube film. The first electrode andthe second electrode are separately disposed on the carbon nanotube filmat a certain distance and electrically connected thereto. The carbonnanotube film includes a plurality of carbon nanotubes isotropicallyarranged, arranged along a fixed direction, or arranged along differentdirections.

Other advantages and novel features of the present sheet-shaped heat andlight source, the method for making the same, and a method for heatingobject adopting the same will become more apparent from the followingdetailed description of present embodiments when taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present sheet-shaped heat and light source, themethod for making the same, and a method for heating object adopting thesame can be better understood with reference to the following drawings.The components in the drawings are not necessarily to scale, theemphasis instead being placed upon clearly illustrating the principlesof the present sheet-shaped heat and light source, the method for makingthe same, and a method for heating an object adopting the same.

FIG. 1 is a schematic view of a sheet-shaped heat and light source, inaccordance with the present embodiment.

FIG. 2 is a cross-sectional schematic view of FIG. 1 along a lineII-II′.

FIG. 3 is a flow chart of a method for making the sheet-shaped heat andlight source shown in FIG. 1.

FIG. 4 shows a Scanning Electron Microscope (SEM) image of a carbonnanotube film including isotropic carbon nanotubes formed by the methodof FIG. 3, and

FIG. 5 shows a Scanning Electron Microscope (SEM) image of a carbonnanotube film formed by the method of FIG. 3 wherein the carbon nanotubefilm has a preferred orientation.

FIG. 6 is a schematic view of heating an object using the sheet-shapedheat and light source shown in FIG. 1.

FIG. 7 is a cross-sectional schematic view of FIG. 6 along a lineVII-VII′.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate at least one present embodiment of the sheet-shaped heat andlight source, the method for making the same, and a method for heatingobject adopting the same, in at least one form, and suchexemplifications are not to be construed as limiting the scope of thedisclosure in any manner.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference will now be made to the drawings, in detail, to describeembodiments of the sheet-shaped heat and light source, the method formaking the same, and a method for heating an object adopting the same.

Referring to FIGS. 1 and 2, a sheet-shaped heat and light source 10 isprovided in the present embodiment. The sheet-shaped heat and lightsource 10 includes a first electrode 12, a second electrode 14, a carbonnanotube film 16, and a base 18. The first electrode 12 and the secondelectrode 14 are separately disposed on the carbon nanotube film 16 at acertain distance apart and electrically connected thereto.

Further, the carbon nanotube film 16 includes a plurality of carbonnanotubes parallel arranged and orientated therein, thereby the carbonnanotubes of the carbon nanotube film 16 having a fixed orientation,that is, parallel to a surface of the carbon nanotube film 16. Thecarbon nanotubes are isotropically arranged along a fixed direction, orarranged along different directions. The adjacent carbon nanotubes arecombined and attracted by van der Waals attractive force, therebyforming a free-standing structure. As such, the carbon nanotube film 16has good tensile strength, and can, advantageously, be formed into mostany desired shape, and so, opportunely, can have a planar or curvedstructure.

Length and width of the carbon nanotube film 16 is not limited. It canbe made with any desired length or width according to practical needs.In the present embodiment, a thickness of the carbon nanotube film 16 isin an approximate range from 1 micrometer to 1 millimeter. In thepresent embodiment, the carbon nanotube film 16 is planar. The carbonnanotubes in the carbon nanotube film 16 are arranged along differentdirections. A length of each carbon nanotube film is about 30centimeters. A width of each carbon nanotube film is about 30centimeters. A thickness of each carbon nanotube film is about 50micrometers.

It is to be understood that the carbon nanotube film 16 can,advantageously, be replaced by a carbon nanotube layer. The carbonnanotube layer can, opportunely, include many layers of carbon nanotubefilms overlapping each other to form an integrated carbon nanotube layerwith an angle of α, and α is the angle of difference between the twoorientations of carbon nanotubes of the two adjacent and overlappedcarbon nanotube films, 0≦α≦90°. The specific degree of a depends onpractical needs. That is, the nanotubes of one carbon nanotube film areoriented in a same direction and the nanotubes in an adjacent andoverlapped carbon nanotube film are all oriented in a direction 0-90degrees different from the first film. The first electrode 12 and thesecond electrode 14 are separately disposed on the carbon nanotube layerat a certain distance, and electrically connected to the carbon nanotubelayer.

Moreover, the first electrode 12 and the second electrode 14 can,opportunely, be disposed on a same surface or opposite surfaces of thecarbon nanotube film 16. Further, the first electrode 12 and the secondelectrode 14 are separated at a certain distance to form a certainresistance therebetween, thereby preventing short circuits in use.

In the present embodiment, because of the adhesive properties of carbonnanotube film, the first electrode 12 and the second electrode 14 aredirectly attached to the carbon nanotube film 16, and thereby forming anelectrical contact therebetween. Moreover, the first electrode 12 andthe second electrode 14 are attached on the same surface of the carbonnanotube film 16 by a conductive adhesive. Quite suitably, theconductive adhesive material is silver adhesive. It should be noted thatany other bonding ways can be adopted as long as the first electrode 12and the second electrode 14 are electrically connected to the carbonnanotube film 16.

The base 18 can be ceramic, glass, resin, or quartz. The base 18 is usedto support the carbon nanotube film 16. The shape of the base 18 can bedetermined according to practical needs. In the present embodiment, thebase 18 is a ceramic substrate. Due to the carbon nanotube film 16having a free-standing property, in practice, the sheet-shaped heat andlight source 10 can, benefically, be without the base 18.

Referring to FIG. 3, a method for making the above-describedsheet-shaped heat and light source 10 are provided in the presentembodiment. The method includes the steps of: (a) providing an array ofcarbon nanotubes formed on a substrate; (b) providing a pressing deviceto press the array of carbon nanotubes, thereby forming a carbonnanotube film 16; and (c) providing a first electrode and a secondelectrode separately disposed on a same surface or opposite surfaces ofthe carbon nanotube film and electrically connected thereto, therebyforming the sheet-shaped heat and light source 10.

In step (a), an array of carbon nanotubes, quite suitably, asuper-aligned array of carbon nanotubes is provided. The givensuper-aligned array of carbon nanotubes can be formed by the steps of:(a1) providing a substantially flat and smooth substrate; (a2) forming acatalyst layer on the substrate; (a3) annealing the substrate with thecatalyst layer in air at a temperature in the approximate range from700° C. to 900° C. for about 30 to 90 minutes; (a4) heating thesubstrate with the catalyst layer to a temperature in the approximaterange from 500° C. to 740° C. in a furnace with a protective gastherein; and (a5) supplying a carbon source gas to the furnace for about5 to 30 minutes and growing a super-aligned array of carbon nanotubes onthe substrate.

In step (a1), the substrate can, beneficially, be a P-type siliconwafer, an N-type silicon wafer, or a silicon wafer with a film ofsilicon dioxide thereon. Preferably, a 4-inch P-type silicon wafer isused as the substrate.

In step (a2), the catalyst can, advantageously, be made of iron (Fe),cobalt (Co), nickel (Ni), or any alloy thereof.

In step (a4), the protective gas can, beneficially, be made up of atleast one of nitrogen (N₂), ammonia (NH₃), and a noble gas. In step(a5), the carbon source gas can be a hydrocarbon gas, such as ethylene(C₂H₄), methane (CH₄), acetylene (C₂H₂), ethane (C₂H₆), or anycombination thereof.

The super-aligned array of carbon nanotubes can, opportunely, have aheight above 100 micrometers and include a plurality of carbon nanotubesparallel to each other and approximately perpendicular to the substrate.Because the length of the carbon nanotubes is very long, portions of thecarbon nanotubes are bundled together. Moreover, the super-aligned arrayof carbon nanotubes formed under the above conditions is essentiallyfree of impurities such as carbonaceous or residual catalyst particles.The carbon nanotubes in the super-aligned array are closely packedtogether by the van der Waals attractive force.

In step (b), a certain pressure can, beneficially, be applied to thearray of carbon nanotubes by the pressing device. In the process ofpressing, the carbon nanotubes in the array of carbon nanotubes form thecarbon nanotube film 16 under pressure. Quite suitably, the carbonnanotubes are nearly all parallel to a surface of the carbon nanotubefilm 16.

In the present embodiment, the pressing device can, advantageously, be apressure head. The pressure head has a glossy surface. It is to beunderstood that, the shape of the pressure head and the pressingdirection can, opportunely, determine the direction of the carbonnanotubes arranged therein. Specifically, referring to FIG. 4, when aplanar pressure head is used to press the array of carbon nanotubesalong the direction perpendicular to the substrate, a carbon nanotubefilm having a plurality of carbon nanotubes isotropically arranged can,advantageously, be obtained. Referring to FIG. 5, when a roller-shapedpressure head is used to press the array of carbon nanotubes along afixed direction, a carbon nanotube film having a plurality of carbonnanotubes aligned along the fixed direction is obtained. When aroller-shaped pressure head is used to press the array of carbonnanotubes along different directions, a carbon nanotube film having aplurality of carbon nanotubes aligned along different directions isobtained.

Understandably, in the process of pressing, the carbon nanotubes will,benefically, tilt, thereby forming a carbon nanotube film having afree-standing structure. The carbon nanotubes in the free-standingstructure are nearly all parallel to a surface of the carbon nanotubefilm, and are isotropically arranged, arranged along a fixed direction,or arranged along different directions.

It is to be understood that, a degree of the slant of the carbonnanotubes in the carbon nanotube film 16 is related to the pressure. Thegreater the pressure, the greater the degree of slant. A thickness ofthe carbon nanotube film 16 is opportunely determined by the height ofthe carbon nanotube array and the pressure. That is, the greater theheight of the carbon nanotube array and the less the pressure, thelarger the thickness of the carbon nanotube film 16.

Quite usefully, the carbon nanotube film 16 can be treated with anorganic solvent. The organic solvent is volatilizable and can beethanol, methanol, acetone, dichloroethane, or chloroform. Quitesuitably, the organic solvent is dropped on the carbon nanotube film 16through a dropping tube in the present embodiment. After soaking, in theorganic solvent, the carbon nanotube segments in the carbon nanotubefilm 16 will, at least, partially be formed into carbon nanotube bundlesdue to the surface tension of the organic solvent. Due to the decreaseof the surface area, the carbon nanotube film 16 loses viscosity butmaintains high mechanical strength and toughness.

Further, the carbon nanotube film 16 can be overlapped on another arrayof carbon nanotubes, by repeating the step (b), thereby forming a carbonnanotube layer containing two carbon nanotube films. The two carbonnanotube films in the carbon nanotube layer are overlapped and coupledby van der Waals attractive force. As such, the carbon nanotube layerincluding several carbon nanotube films can, opportunely, be obtained.

It is to be noted that, the carbon nanotube films can, beneficially, beoverlapped to form a carbon nanotube layer. Quite suitably, the pressingdevice can, opportunely, be used to press the carbon nanotube films,thereby forming the carbon nanotube layer.

In practical use, the carbon nanotube film 16 can, beneficially, bedisposed on a base 18. The base 18 can be ceramic, glass, resin, orquartz. The base 18 is used to support the carbon nanotube film 16. Theshape of the base 18 can be determined according to practical needs. Inthe present embodiment, the base 18 is a ceramic substrate. Moreover,due to the carbon nanotube film 16 having a free-standing property, inpractice, the carbon nanotube film 16 can, opportunely, be used in thesheet-shaped heat and light source 10 without the base 18.

In a process of using the sheet-shaped heat and light source 10, when avoltage is applied to the first electrode 12 and the second electrode14, the carbon nanotube film 16 of the sheet-shaped heat and lightsource 10 emits electromagnetic waves with a certain wavelength. Quitesuitably, when the carbon nanotube film 16 of the sheet-shaped heat andlight source 10 has a fixed surface area (length*width), the voltage andthe thickness of the carbon nanotube film 16 can, opportunely, be usedto make the carbon nanotube film 16 emit electromagnetic waves atdifferent wavelengths. If the voltage is fixed at a certain value, theelectromagnetic waves emitting from the carbon nanotube film 16 areinversely proportional to the thickness of the carbon nanotube film 16.That is, the greater the thickness of carbon nanotube film 16, theshorter the wavelength of the electromagnetic waves. Further, if thethickness of the carbon nanotube film 16 is fixed at a certain value,the greater the voltage applied to the electrode, the shorter thewavelength of the electromagnetic waves. As such, the sheet-shaped heatand light source 10, can be easily configured to emit a visible lightand create general thermal radiation or emit infrared radiation.

Due to carbon nanotubes having an ideal black body structure, the carbonnanotube film 16 has excellent electrical conductivity, thermalstability, and high thermal radiation efficiency. The sheet-shaped heatand light source 10 can, advantageously, be safely exposed, while inuse, to oxidizing gases in a typical environment. When a voltage of 10volts˜30 volts is applied to the electrodes, the sheet-shaped heat andlight source 10 emits electromagnetic waves. At the same time, thetemperature of sheet-shaped heat and light source 10 is in theapproximate range from 50° C. to 500° C.

In the present embodiment, the surface area of the carbon nanotube film16 is 900 square centimeters. Specifically, both the length and thewidth of the carbon nanotube film 16 are 30 centimeters. The carbonnanotube film 16 includes a plurality of carbon nanotubes isotropicallyarranged along a fixed direction, or arranged along differentdirections.

Further, quite suitably, the sheet-shaped heat and light source 10 isdisposed in a vacuum device or a device with inert gas filled therein.When the voltage is increased in the approximate range from 80 volts to150 volts, the sheet-shaped heat and light source 10 emitselectromagnetic waves such as visible light (i.e. red light, yellowlight etc), general thermal radiation, and ultraviolet radiation.

It is to be noted that the sheet-shaped heat and light source 10 can,beneficially, be used as electric heaters, infrared therapy devices,electric radiators, and other related devices. Moreover, thesheet-shaped heat and light source 10 can, beneficially, be used as anoptical device, and thereby being used as light sources, displays, andother related devices.

Referring to FIGS. 6 and 7, a method for heating an object adopting theabove-described sheet-shaped heat and light source 20 is also described.In the present embodiment, the sheet-shaped heat and light source 20includes a first electrode 22, a second electrode 24, and a carbonnanotube film 26, curved to form a hollow cylinder. Further, the firstelectrode 24 and the second electrode 26 are separately disposed on thecarbon nanotube film 26 at a certain distance apart and electricallyconnected thereto.

Further, the surface area of the carbon nanotube film 26 is 900 squarecentimeters. Specifically, both the length and the width of the carbonnanotube film 26 are 30 centimeters. The carbon nanotube film 26includes a plurality of carbon nanotubes isotropically arranged,arranged along a fixed direction, or arranged along differentdirections. The voltage applied to the electrode 12 and the electrode 14is 15 volts. The temperature of the sheet-shaped heat and light source10 is about 300° C.

Due to the carbon nanotube film 26 having a free-standing property, thesheet-shaped heat and light source 20 can have no base. Because thecarbon nanotube film 26 has excellent tensile strength, the sheet-shapedheat and light source 10 has advantageously a ring-shaped or a hollowcylinder-shaped carbon nanotube film 26. Quite suitably, in the processof heating the object 30, the object 30 and the carbon nanotube film 26are directly contacted with each other or apart from each other at acertain distance as required.

The method for heating an object using the sheet-shaped heat and lightsources 20 includes the steps of: providing an object 30; disposing acarbon nanotubes layer 26 of the sheet-shaped heat and light source 20to a surface of the object 30; and applying a voltage between the firstelectrode 22 and the second electrode 24 to heat the object 30.

It is to be understood that the above-described embodiments are intendedto illustrate rather than limit the disclosure. Variations may be madeto the embodiments without departing from the spirit of the disclosureas claimed. It is understood that any element of any one embodiment isconsidered to be disclosed to be incorporated with any other embodiment.The above-described embodiments illustrate the scope of the disclosurebut do not restrict the scope of the disclosure.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. It is also to be understood that the description and the claimsdrawn to a method may include some indication in reference to certainsteps. However, the indication used is only to be viewed foridentification purposes and not as a suggestion as to an order for thesteps.

What is claimed is:
 1. A method for making a sheet-shaped heat and lightsource, the method comprising: providing an array of carbon nanotubes ona substrate; forming a carbon nanotube film by pressing the array ofcarbon nanotubes; and electrically connecting a first electrode and asecond electrode with the carbon nanotube film.
 2. The method of claim1, wherein the providing the array of carbon nanotubes on the substratecomprises: forming a catalyst layer on the substrate; annealing thesubstrate with the catalyst layer in air; heating the substrate with thecatalyst layer in a furnace filled with a protective gas; and supplyinga carbon source gas to the furnace.
 3. The method of claim 1, whereinthe annealing the substrate with the catalyst layer is performed at atemperature in a range from about 700° C. to about 900° C. for a time ina range from about 30 minutes to about 90 minutes.
 4. The method ofclaim 1, wherein the heating the substrate with the catalyst layer isperformed at a temperature in a range from about 500° C. to about 740°C.
 5. The method of claim 1, wherein the supplying the carbon source gasto the furnace is performed for a time in a range from about 5 minutesto about 30 minutes.
 6. The method of claim 1, wherein the pressing thearray of carbon nanotubes comprises pressing the array of carbonnanotubes with a planar pressure head.
 7. The method of claim 6, whereinthe pressing the array of carbon nanotubes comprises pressing the arrayof carbon nanotubes along a direction perpendicular to the substratewith the planar pressure head.
 8. The method of claim 1, wherein thepressing the array of carbon nanotubes comprises pressing the array ofcarbon nanotubes with a roller-shaped pressure head.
 9. The method ofclaim 8, wherein the pressing the array of carbon nanotubes comprisesrolling the array of carbon nanotubes along a fixed direction with theroller-shaped pressure head.
 10. The method of claim 8, wherein thepressing the array of carbon nanotubes comprises rolling the array ofcarbon nanotubes along different directions with the roller-shapedpressure head.
 11. The method of claim 1, further comprising treatingthe carbon nanotube film with an organic solvent after forming thecarbon nanotube film.
 12. The method of claim 11, wherein the organicsolvent is ethanol, methanol, acetone, dichloroethane, or chloroform.13. The method of claim 1, further comprising locating the carbonnanotube film on a base after forming the carbon nanotube film.
 14. Themethod of claim 1, wherein the electrically connecting the firstelectrode and the second electrode with the carbon nanotube filmcomprises electrically connecting the first electrode and the secondelectrode with the carbon nanotube film by a conductive adhesive. 15.The method of claim 1, wherein the electrically connecting the firstelectrode and the second electrode with the carbon nanotube filmcomprises locating the first electrode and the second electrode on asurface of the carbon nanotube film.
 16. A method for making asheet-shaped heat and light source, the method comprising: providing acarbon nanotube film; curving the carbon nanotube film to form a hollowcylinder; and electrically connecting a first electrode and a secondelectrode with the carbon nanotube film.
 17. The method of claim 16,wherein the electrically connecting the first electrode and the secondelectrode with the carbon nanotube film comprises locating the firstelectrode and the second electrode on a surface of the hollow cylinder,and the first electrode and the second electrode are spaced from eachother.
 18. A method for heating an object, the method comprising:providing a sheet-shaped heat and light source, the sheet-shaped heatand light source comprising: a carbon nanotube film curved to form ahollow cylinder; and at least two electrodes spaced from each other,located on a surface of the hollow cylinder and electrically connectedto the carbon nanotube film; placing an object in the hollow cylinder;and supplying a voltage between the at least two electrodes.
 19. Themethod of claim 18, wherein the carbon nanotube film and the object aredirectly in contact with each other.
 20. The method of claim 18, whereinthe carbon nanotube film and the object are spaced from each other.